The classical cannabinoid, delta-9-tetrahydrocannabinol (Δ9-THC), is the major active constituent extracted from Cannabis sativa. The effects of cannabinoids are due to an interaction with specific high-affinity receptors. Presently, two cannabinoid receptors have been characterized: CB1, a central receptor found in the mammalian brain and a number of other sites in the peripheral tissues; and CB2, a peripheral receptor found principally in cells related to the immune system. In addition, it has recently been reported that the GPR55 orphan receptor binds cannabinoid type ligands and has been proposed as a third receptor subtype. The CB1 receptor is believed to mediate the psychoactive properties, associated with classical cannabinoids. Characterization of these receptors has been made possible by the development of specific synthetic ligands such as the agonists WIN 55212-2 and CP 55,940.
In addition to acting at the cannabinoid receptors, cannabinoids such as Δ9-THC also affect cellular membranes, thereby producing undesirable side effects such as drowsiness, impairment of monoamine oxidase function, and impairment of non-receptor mediated brain function. The addictive and psychotropic properties of some cannabinoids also limit their therapeutic value.
The pharmacological effects of cannabinoids pertain to a variety of areas such as the central nervous system, the cardiovascular system, the immune system and/or endocrine system. More particularly, compounds possessing an affinity for either the CB1 or the CB2 cannabinoid and potentially the GPR55 receptors are useful as agents: acting on the central nervous system and immunomodulators; in thymic disorders; vomiting; myorelaxation; various types of neuropathy; memory disorders; dyskinesia; migraine; multiple sclerosis; asthma; epilepsy; glaucoma; in anticancer chemotherapy; in ischemia and angor; in orthostatic hypotension; and in cardiac insufficiency.
A number of bi- and tri-cyclic cannabinoids are described in U.S. Pat. No. 7,057,076 to Makriyannis et al., but these are structurally distinct of the compounds of the present invention. Makriyannis identifies a range of binding affinities for two or more compounds, but does not provide any supporting data that shows the binding data of individual compounds on both the CB-1 and CB-2 receptors. It is difficult to assess, therefore, whether there is truly selectivity of the compounds for one receptor over another.
There still remains a need for identifying compounds that can be used for therapeutic purposes to affect treatment of conditions or disorders that are mediated by the CB-1 receptor and/or the CB-2 receptor.